(CNN) -- An audio message purportedly from al Qaeda leader Osama bin Laden -- the second in three days -- says Arab leaders "sacrificed" Palestinians and calls on bin Laden's followers once again to liberate Palestine.

This image accompanied a message from Osama bin Laden in November.

In the message, posted Sunday on radical Islamist Web sites known for posting statements from bin Laden, the speaker states: "Even if all the leaders have sacrificed the Palestinian issue in its entirety, we are not relieved of the responsibility. ... Each one of us is responsible for the death of our people in Gaza."

The speaker also calls on Egyptian militants to end the blockade of Gaza: "They are the only ones close to its borders, and they must work on breaking this siege. "

The message seemed to be a follow-up to a similar statement Friday, in which the speaker reiterated jihadist opposition to the existence of the Jewish state and its policies, and told listeners that "liberating" Palestine should be the aim of every Muslim.

A U.S. intelligence official said the CIA is looking into Sunday's purported bin Laden message and analyzing it to determine if it is indeed bin Laden's voice. The official spoke anonymously because he is not authorized to speak on the record.